A biofuel cell that has an oxidoreductase immobilized as a catalyst on at least one electrode of an anode and a cathode can efficiently extract electrons from fuel such as glucose or ethanol, which cannot be used as a general industrial catalyst. Accordingly, biofuel cells are drawing attention as next-generation fuel cells with a large capacity and a high level of safety.
FIG. 7A is a diagram showing a reaction scheme of the anode of a biofuel cell. FIG. 7B is a diagram showing a reaction scheme of the cathode of the biofuel cell. As shown in FIGS. 7A and 7B, in a biofuel cell using glucose as fuel, an oxidation reaction of glucose progresses at the anode, and a reduction reaction of oxygen (O2) in the atmosphere progresses at the cathode. At the anode, electrons are transferred in the following order: glucose, glucose dehydrogenase, nicotinamide adenine dinucleotide (NAD+), diaphorase, the electron mediator, and the electrode (carbon).
In this manner, a biofuel cell can use a carbohydrate, such as glucose, as fuel. Accordingly, commercially available beverages and the like can be used as fuel, and apparatuses that can use beverages have been suggested (see Patent Documents 1 and 2, for example).